fix: the CLI's agent default could not write (#165)

src/agent_harness/__main__.py

@@ -888,6 +888,7 @@ def main(argv: list[str] | None = None) -> int:
     # starts for `--help` on a machine with no queue and no credentials, and
     # only the default value is needed to print it.
     from .executor import DEFAULT_CONTEXT_BUDGET
+    from .session_executor import DEFAULT_AGENT_COMMAND
 
     parser = argparse.ArgumentParser(prog="agent-harness", description=__doc__)
     parser.add_argument(
@@ -1123,9 +1124,17 @@ def main(argv: list[str] | None = None) -> int:
     )
     p_run.add_argument(
         "--agent",
-        default="claude -p {prompt_file}",
+        # The executor's default, not a second one. They disagreed: the
+        # executor's carried `--permission-mode acceptEdits` and the CLI's did
+        # not, so `run --session-host` without this flag produced an agent that
+        # could not write. It reported no changes and read as a model that had
+        # considered the task and declined — measured, and it cost a run.
+        default=" ".join(DEFAULT_AGENT_COMMAND),
         metavar="CMD",
-        help="CLI agent to run per item. `{prompt_file}` is substituted.",
+        help="CLI agent to run per item. `{prompt_file}` is substituted. "
+        "Defaults to the agent command the session executor declares, which "
+        "grants edit permission — an agent that cannot write reports no "
+        "changes, which is indistinguishable from one that chose to make none.",
     )
     p_run.add_argument("--limit", type=int, help="stop after N items")
     p_run.add_argument(

tests/test_cli_roles.py

@@ -287,3 +287,33 @@ def capture(self: Any, method: str, url: str, **kwargs: Any) -> Any:
     assert "timeout" not in sent["json"] and "role" not in sent["json"]
     assert sent["headers"]["x-api-key"] == "shared-key"
     assert "Authorization" not in sent["headers"]
+
+
+def test_the_cli_agent_default_is_the_executor_s() -> None:
+    """They disagreed, and the CLI's was the one that could not write.
+
+    `session_executor.DEFAULT_AGENT_COMMAND` carries `--permission-mode
+    acceptEdits`; the CLI's `--agent` default did not. So `run --session-host`
+    without the flag produced an agent that was refused every Edit, reported
+    no changes, and read as a model that had considered the task and declined.
+
+    Measured: it cost a full agent run, and the agent's own account of the
+    refusal sat in a scrollback nothing reads.
+
+    Asserted against the source rather than a parsed value, because the defect
+    was *a second default existing at all* — a literal here that happens to
+    match today would drift again tomorrow.
+    """
+    import inspect
+
+    from agent_harness import __main__
+    from agent_harness.session_executor import DEFAULT_AGENT_COMMAND
+
+    source = inspect.getsource(__main__)
+    assert 'default=" ".join(DEFAULT_AGENT_COMMAND)' in source, (
+        "the CLI must take the executor's agent command, not declare its own"
+    )
+    assert '"--permission-mode"' in inspect.getsource(
+        __import__("agent_harness.session_executor", fromlist=["x"])
+    ), "and that command must still grant edit permission"
+    assert "--permission-mode" in " ".join(DEFAULT_AGENT_COMMAND)